The present invention relates to an image forming apparatus and more particularly to an image forming apparatus capable of not only giving display images but also formed an original to be copied by an electrophotographic process.
In the conventional image forming apparatus having the above-described capabilities, there has been used a liquid crystal panel with a simple matrix construction in which a large number of stripe electrodes are opposed in the horizontal and vertical directions and a liquid crystal is sandwiched therebetween. However, the liquid crystal panel of the type described has a defect that the amount of information to be displayed cannot be increased sufficiently because of the limits imposed on the operation of a liquid crystal. Meanwhile, as a means for increasing the amount of information to be displayed, there has been recently developed a device in which a thin film transistor (to be referred to as "TFT" hereinafter in this specification) is provided for each picture element and such TFTs are arranged into a matrix array. However, the increase in amount of information to be displayed means the reduction in size of picture elements in the case of an image forming apparatus with a predetermined display picture area. When this is used as a reflection type, there is a defect that a double image or two separated picture element images are formed by an image forming part of a liquid crystal layer produced by optical changes and by a shadow part formed by the projection of an optically changing part upon a light scattering reflection surface by an external illumination.
Furthermore, when a reflection optical system is used to display and to impart a light image to an electrophotographic printer by utilizing such a liquid crystal panel, there is a defect that such a metal forming electrodes gives to a reflecting plate a shadow which lowers a display potential. No scattered light rays are emitted from this metal electrode so that there is a defect that a black part is printed on a copied recording medium. Furthermore, when such a liquid panel is used as a display panel, such metal electrodes function as a reflecting surface, making it difficult to view a display.